The invention is based on a priority application EP06115704.6 which is hereby incorporated by reference.
The invention relates to a method for a handover procedure of a user terminal on radio interfaces according to the preamble of claim 1, a base station according to the preamble of claim 9, and a network according to the preamble of claim 10.
Orthogonal frequency division multiplexing (OFDM) radio systems are currently under discussion in many places as e.g. in Third Generation Partnership Project Long Term Evolution (3GPP LTE), the WiFi standard IEEE 802.11 or the WiMax standard IEEE 802.16.
For the UMTS LTE (UMTS LTE=Universal Mobile Telecommunication System Long Term Evolution), it is currently discussed, how the access procedure shall be performed on a high level. The evolved UTRAN Node B (UTRAN=UMTS Terrestrial Radio Access Network), called eNodeB, to which the user terminal will switch is called the target eNodeB or target base station, while the old eNodeB, from which the user terminal will leave is called the source eNodeB or source base station.
During any (hard) handover in a mobile communications network, the user terminal, i.e. the User Equipment (UE) in UMTS, has to change its communication link(s) to another eNodeB. For this purpose so-called Random Access Channels (RACH) are provided on each air interface. The user terminal first listens to the frame structure of the target air interface to gather synchronisation with the target eNodeB. Then the Random Access Channel is used to send the first message from the user terminal to the target eNodeB. From this point in time the user terminal is associated with the target eNodeB and the message exchange is performed.